1. Field of the Invention
This invention relates to the art of electrical acceleration switches of the type having a mass movable in a housing against a spring bias in response to an applied force, and more particularly concerns a miniature omnidirectional switch instantly responsive to an impact of sufficient magnitude to open normally closed contacts in the switch.
2. Description of the Art
A typical miniature acceleration switch of a type described in prior U.S. Pat. Nos. 4,746,774, and 4,789,762 has a cylindrical shell or housing closed by a header at one end. In the shell is a cylindrical mass movable axially or tiltable laterally against spring bias in response to forces of acceleration applied to the housing and mass. The displaced electrically conductive mass closes a normally open electric circuit between spaced electrically conductive terminals.
The prior miniature acceleration switches have been found to respond too slowly to an applied impact in applications where the switch must respond to an impact in less than 200 microseconds. In the prior switches the electrical contacts are normally open and are spaced apart sufficiently so that externally applied random vibrations do not cause the switch contacts to close. The time required for the mass to move to close the open contacts upon application of an actuating force is several milliseconds or longer. The switch cannot respond fast enough where the response time must be 0.2 of a millisecond or less. Another disadvantage of the prior switches is that they are normally open and are not useable in applications where the switch contacts must be normally closed. Some of the prior switches are limited to respond to forces directed only axially of the housings in which the masses move. Other switches are limited to respond only to forces directed laterally or angularly to the axes of the housings.